Defo a XP-120 for decent temps and the ability to overclock! someone at o-cuk has one with a 120mm delta and gets ambient temps at 100% CPU load and 1.6v under the belt of his CPU! Seriously good sink!

As BUFF points out, the Thermalright stuff is exceptional as far as performance goes but it may not fit your motherboard.

"Best" is pretty meaningless though without first stating your criteria. Do you want the best (performance) cooling? The best (lowest price) price? The best (bang for your buck) value? The best (easy to install) installation? The quietest? These are all DIFFERENT HSFs.

The best performance is the XP-120 with a 120mm fan pushing 170+CFM. This is as good as aircooling gets, but it's expensive, noisey, a pain to install and it may not fit your motherboard at all even with mods.

The Zalman cools pretty good and it's quiet but it is not much better then stock on performance and it's no bargain. It also doesn't mount very securely and is totally unsuitable for CPUs without heat spreaders. Can damage the core easily. It's easy to mount and very quiet though, but since the fan doesn't move that much air you're better off with the aluminum/copper version rather than the straight copper.

Overall I am a huge fan of the Thermalright Venus 12. Fits every motherboard, very good performance (probably better than many of the Thermalright XP-90s and XP-120s depending on the fans you use on the XPs), super easy to install, includes 2 potentiometers to adjust the fan from 2000RPM to nearly 6000RPM, includes the fan, mounts super easily and solidly and is less than half the cost of an XP-120 and a good fan. Much less than half usually.

If you're not into overclocking at all just about any HSF will be sufficient, as the A64 runs super cool when not overclocked.

Firelord:

CPUs running at ambient on air is a physical impossibility, even when idle, let alone at full load. He's not measuring his temps accurately.

The Venus is very quiet when you turn the RPM below 4000 and it is nearly silent at 2000 RPM. It cools much better though when you crank it up to nearly 80 CFM, but it's pretty loud. There is no such thing as silent air cooling that is high performance. If you want that the best you can do is an XP-120 with a 120mm fan running less than 2300 RPM. This will not cool as well as the Venus on high but it will be pretty good and reasonably quiet. Still very pricey though, and you may have trouble mounting it depending on which motherboard you use.

The MSI K8N Neo2 has a pretty crappy layout. The Venus is super easy to install and is a much more sensible option to me, but it is not quiet at all. It is the value leader in high performance air cooling I believe.

Assuming the Venus is essentially the same as the Volcano, I can recommend the Thermaltake Venus - my Volcano is relatively quiet at low speeds while still cooling pretty well, and is very good at cooling at moderate noises (before the noises start to get irritating!)

"Well, there was your Uncle Tiberius who died wrapped in cabbage leaves but we assumed that was a freak accident."